A polarizing plate is an optical diode for converting natural light or predetermined polarization into polarization in a specific direction, and is extensively used in a display device such as a liquid crystal display and an organic light emitting diode (OLED). The polarizing plate recently used in the display device has been generally used in a structure where a protection film is laminated on both surfaces of a polarizer formed of a polyvinyl alcohol (hereinafter, referred to as ‘PVA’)-based resin dyed with a dichromatic dye or iodine.
However, in accordance with a recent trend of reducing a thickness of display devices, the polarizing plate also needs to have a reduced thickness. Accordingly, a technology of manufacturing a single-faced polarizing plate where a protection film is attached to only one surface of the polarizer, a technology of forming a polyvinyl alcohol-based film (hereinafter, referred to as ‘PVA’) having a small thickness of 50 μm or less, which is the polarizer, or the like is proposed.
However, in an existing method for manufacturing a single-faced polarizing plate, in which a protection film is supplied to one surface of the PVA, an adhesive composition is applied therebetween, and pressing is performed by using a pressing roll, it is difficult to manufacture. The reason is that in a process of applying the adhesive composition, in the case where a width of the adhesive composition applied is smaller than a width of a polarizer, a non-attachment surface is formed on the polarizer and a PVA-based film having the non-attachment surface is stripped when post-processing is performed. Accordingly, in order to prevent the problem, the adhesive composition is applied in a width that is more widely than the width of the polarizer, but in this case, the adhesive applied in the width that is more widely than the width of the polarizer contaminates the pressing roll in a pressing process.
Meanwhile, in view of reducing a thickness, it is most preferable to manufacture the single-faced polarizing plate by using the PVA-based film having the small thickness. However, in the case where the existing method for manufacturing the single-faced polarizing plate is directly applied to the thin PVA-based film having the thickness of 50 μm or less, which has low rigidity in a TD direction due to stretching, the single-faced polarizing plate is easily broken due to a difference between moduli applied to both surfaces of the PVA-based film.
Accordingly, there is a demand for developing a technology by which in a process of manufacturing the single-faced polarizing plate, the thin polarizer having the thickness of 50 μm or less can be used, and even though the width of the adhesive composition applied is slightly larger than the width of the polarizer, the occurrence of contamination can be easily and simply prevented in the manufacturing process.